(1) Field of the Invention
The invention relates to a method of metallization of an integrated circuit device, and more particularly, to an aluminum plug metallization method having low cost, low resistance, and few process steps in the manufacture of an integrated circuit device.
(2) Description of the Prior Art
In the fabrication of integrated circuit devices, metal layers make contact to lower conductive layers of the integrated circuit through vias in an insulating layer. Aluminum or an aluminum alloy is often used as the interconnection metal. However, the sputtering process used to apply the aluminum often results in incomplete filling of the via openings due to poor step coverage. Large aluminum grains tend to form on the surface of the insulating layer within the via openings, causing voids. The metal film cannot be melted using rapid thermal annealing (RTA) or furnace methods because of pollution problems. That is, the metal film will flow and become uncontrollable. It will adhere to the walls of the annealing chamber and cause pollution problems. The traditional hot aluminum sputtering method cannot control the grain size of the aluminum, causing metal line formation problems.
Various methods have been proposed to improve aluminum via filling. U.S. Pat. Nos. 5,356,836 to Chen et al, 5,288,665 to Nulman, and 5,171,412 to Talieh et al teach deposition of aluminum in stages at different temperatures. U.S. Pat. No. 5,512,512 to Isobe teaches reflow of the aluminum and U.S. Pat. No. 5,071,791 to Inoue et al teaches heating the wafer while depositing the aluminum. U.S. Pat. No. 4,756,810 to Lamont, Jr. et al discloses radio frequency (RF) excitation to mobilize deposited aluminum to fill holes. In the paper, "A Novel High Pressure Low Temperature Aluminum Plug Technology For Sub-0.5 .mu.m Contact/Via Geometries," by Dixit et al, IEDM 1994, pp. 5.3.1-5.3.4, the authors disclose a method of pressurizing a chamber with Argon to force previously deposited AlCu into via holes. The paper, "A Novel 0.25 .mu.m Via Plug Process Using Low Temperature CVD Al/TiN" by Dixit et al, IEDM 1995, pp. 10.7.1-10.7.3 discloses copper doping an aluminum plug by depositing an overlayer of AlCu.